Mendenhall Glacier Facts And other Local Glaciers (updated 3/13/14)

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1 University of Alaska Southeast School of Arts & Sciences A distinctive learning community Juneau Ketchikan Sitka Mendenhall Glacier Facts And other Local Glaciers (updated 3/13/14) This document can be found at Click on Mendenhall Glacier Facts. On that same site is a Google Earth map of the Mendenhall and other glaciers in Google Earth. Mendenhall Glacier Size 2009 Estimated area square km (36.8 square miles) (not including the Mendenhall Towers glacier). Length 21.9 km, (13.6 miles). Widest cross section the upper South Branch 6.2 km (3.8 miles) Ice height at terminus 3-20 meters, (10-70 feet). Terminus width and narrowest part of the glacier 510 meters (0.4 miles) as the raven flies. Terminus exposed to lake, a non-linear 865 meters, (2,835 feet) Elevation at the divide separating the Mendenhall and Taku Glaciers 1,580 meters (5,182 feet). Highest contiguous glacier ice 1,893 meters (6,210 feet). Elevation of Mendenhall Lake 17 meters (56 feet). Lowest bed elevation on the glacier >100 meters (328 feet) below sea level near the North Star Trekking camp elevation 432 meters (1,420 feet). 3 Thickest ice 600 meters (1,968 feet) at the Flux Gate, mid-length on the glacier, below the confluence of the North and South Branches, elevation 680 meters, (2,230 feet) Estimated depth of glacier below Mendenhall Lake level 65 meters (213 feet). Glacier Health Average Terminus Retreat Rates- Across the face of the glacier 2012-winter 2014 ~Unchanged on the lake, 78 meters on the rock outcrop at lake s western edge meters, 406 feet meters, 437 feet meters, 540 feet (255 meters or 836 feet in the center) meters, 194 feet (most from the east side) meters, 253 feet meters, 413 feet meters, 194 feet meters, 554 feet meters, 236 feet meters, 0.7 miles 1760 maximum Little Ice Age extent to km, 3.18 miles Distance from Visitors Center to 2012 terminus 2.4 km, 1.5 miles

2 Average Retreat Rates meters/year, 173 feet/year meters/year, 190 feet/year meters/year, 216 feet/year meters/year, 158 feet/year Ice loss from calving 2.6-4% of total ablation (ice loss) Ice loss area on lower glacier 0.91 square kilometers (0.35 square miles). A glacier s mass balance is the net amount of water equivalent snow and ice that is gained or lost yearly and quantifies glacier health. Surface (excludes calving) 2011 Depth meters/year, volume cubic km/year 2010 Depth meters/year, volume cubic km/year 2005 Depth Depth Depth Depth Depth Depth meters/year, volume cubic km/year (-52,000 Olympic swimming pools/year) Depth meters/year, volume cubic km/year (-32,000 Olympic swimming pools/year). 2 AAR & ELA A healthy stable glacier that is neither advancing nor retreating has approximately >70% of its area at the end of the summer still covered by that prior winter s snowfall. This is called the Accumulation Area Ratio (AAR). The snow line that separates the snow above from the firn (1 yr old snow) or bare glacier ice below is the equilibrium line altitude (ELA). The end-of-summer elevation of the ELA is the best visual indicator of yearly health. Lower ELA s are better for the glacier AAR 63% Average ELA 1036 m, 3,400 feet 2009 AAR 63%, ELA North Branch 915 meters, 3,000 feet; South Branch 1,160 meters 3,800 feet 2008 AAR 73%, ELA 915 meters, 3,000 feet 2007 AAR 45%, ELA 1,225 meters, 4,108 feet 2006 AAR 51%, ELA 1,170 meters, 3,838 feet 2005 AAR 47%, ELA 1,200 meters, 3,936 feet 2004 AAR 42%, ELA 1,250 meters 4,100 feet 2005AAR 29%, ELA 1,370 meters 4,500 feet

3 2000 AAR 80%, ELA 820 meters 2,690 feet 1999 AAR 57%, ELA 1,100 meters 3,608 feet 1998 AAR 42%, ELA 1,250 meters 4,100 feet Miscellaneous Characteristics Surface Ice Speed Maximum ice velocity 160 meters/year, 525 feet/year at the Flux Gate, midlength on the glacier, below the confluence of the North and South Branches, elevation 680 meters, 2,230 feet. 3 Ice velocity at the terminus meters/year, feet/year. 3 Snow Accumulation High elevation snowfall >10 meters, 32.8 feet, water equivalent. 3 Ice Thinning (Melt) Summer terminus melt minimum 2 centimeters (.75 inches)/day, maximum 24 centimeters (9.5 inches), average 12 centimeters (5 inches)/day. 1 Average annual terminus melt 13.3 meters (44 feet) of water at 100 meters (328 feet) elevation. 1 Taku Glacier 2001 Area 775 square km, 300 square miles 6 Length ~60 km, 37.3 miles 1995 Thickest part of glacier 1,477 meters, 4,845 feet Lowest bed elevation ~ 600 meters below sea level, 1,968 feet below sea level Northeast and southwest portions of terminus show signs of thinning 7. Center terminus likely still thickening and advancing Average terminus advance 21 meters/year, 68 feet Average terminus advance 14 meters/year, 46 feet Stopped calving as a push moraine (above sea level sediment) rose in front of glacier thus reducing mass loss ~7.3 km terminus advance, 4.5 miles ~1750 Advanced across Taku River and formed a glacier-dammed lake, dam bursts and retreat begins Depth meters/year, volume loss cubic km/year (-64,000 Norris Glacier 2001 Area 144 square km, 55.6 square miles 6 Lemon Creek Glacier Vicinity Lemon Creek Glacier

4 2001 Area 9.5 square km, 3.6 square miles Depth meters/year, volume loss cubic km/year (-8, Depth meters/year, volume loss cubic km/year (-4,000 Ptarmigan Glacier (west of and adjacent to Lemon Creek Glacier) 2001 Area 1.3 square km, 0.5 square miles 6 Thomas Glacier (viewable up Lemon Creek valley from Egan Drive) 2001 Area 2.9 square km, 1.1 square miles 6 Nugget Creek Glacier 2001 Area 1.9 square km, 0.7 square miles 6 Herbert Glacier 2001 Area 56.5 square km, 21.8 square miles Terminus retreat 37 meters, 120 ft Average terminus retreat 430 meters, 1,430 feet, (39 meters/year, 130 feet/year) km, ~18 meters/year km, ~27 meters/year Little Ice Age Maximum to km, 2.69 miles Eagle Glacier 2001 Area 40.2 square km, 15.5 square miles Average terminus retreat 160 meters, 530 feet meters ~37 meters/year km, Data analysis and compilation by Michael Hekkers, adjunct faculty and staff member. Additional thanks goes to Professors Cathy Connor, Eran Hood at UAS, and Matt Heavner formerly UAS now at Los Alamos National Labs. Numerous current and former UAS students also contributed to these findings including Nick Korzen, David Sauer, Nat Kugler, Ivy Smith, Josh Galbraith and Logan Berner. Thanks to the staff at the Mendenhall Glacier Visitor s Center for their questions, comments, observations and permission to conduct this research. 1 Boyce, E.S., Motyka, R.J., and M. Truffer Flotation and retreat of a lake-calving terminus, Mendenhall Glacier, southeast Alaska, USA. Journal of Glaciology 53(181): Larsen, C.F., Motyka, R.J., Arendt, A.A., Echelmeyer, K.A., and P.E. Geissler Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise. Journal of Geophysical Research 112:F01007, doi: /2006jf Motyka, R.J., O Neel, S., Connor, C.L., and K.A. Echelmeyer Twentieth century thinning of Mendenhall Glacier, Alaska, and its relationship to climate, lake calving, and glacier run-off. Global and Planetary Change 35:

5 4 Courtesy of crevassezone.org, ( ) and measurements made by Michael Hekkers and Roman Motyka ( ). 5 Nolan, M., R.J. Motyka, K. Echelmeyer and D.C. Trabant Ice thickness measurements of Taku Glacier, Alaska, U.S.A., and their relevance to its recent behavior. J. Glaciol., 41(139), National Snow and Ice Data Center, Global Land Ice Measurements from Space. 7 Based on 2009 photographs by Bruce Molnia, USGS. 8 Motyka, R.J. and J.E. Beget Taku Glacier, southeast Alaska, U.S.A.: Late Holocene history of a tidewater glacier. Arct. Alp. Res., 28(1), Lawrence, D.B Glacier Fluctuation for Six Centuries in Southeastern Alaska and Its Relation to Solar Activity. Geographical Review 40(2), Field, W.O Mountain glaciers of the Northern Hemisphere: Hanover, New Hampshire, U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory. 1, 698pp; 2, 932pp.